There are many applications where it is desired to remove particulate matter from water either for ecological reasons or to permit the water to be utilized for a desired purpose. Most commonly, such systems are used in industrial applications, such as paper mills, to remove particulate matter introduced into the water during an industrial process before returning the water to the river, lake, or other body from which it was originally obtained.
The second, and increasingly important, application of such systems is to purify water for domestic use. Such systems are normally utilized by towns or other municipalities.
Water clarification systems are generally of two types, sedimentation systems or flotation systems. Flotation systems require much smaller equipment for the same particle removing capacity, and are therefore preferred. An example of a flotation water clarification system is shown in U.S. Pat. No. 4,022,696 issued May 10, 1977, to Dr. Milos Krofta, the applicant herein.
This system has proved capable of reducing the suspended solids or particles in incoming water initially containing up to 1500 parts per million (ppm) to below 20 ppm. While this results in clarified water satisfactory for most industrial applications, it is still possible to have solid particles in the clarified water which are of a size in excess of 100 to 300 microns. Such particles are big enough to clog shower heads, nozzles, or other very small orifices through which water passes in domestic and some industrial applications.
Therefore, in order to permit flotation water clarification systems of, for example, the type disclosed in the above mentioned Krofta patent to be utilized in domestic and other applications where the water may be required to pass through small orifices, it is necessary that an additional filtering step be performed. Ideally, such filtering would be done in the clarification system. However, particles trappped by the screen or other filtering element reduce clarified water flow and, if the filtering element is not continuously or at least regularly cleaned, would in a short time completely block the filtering element. Also, even if the filter is cleaned, there remains the problem of how to control the buildup of filtered particles. Heretofore, space limitations in the system and the complexity of equipment for effectively cleaning the filtering element(s) and flushing the filtered particles have necessitated that a separate installation be provided for the filtering step with separate tanks, pumps, piping, and other components. Having such a separate facility and separate equipment is costly, both in terms of the additional equipment required and the additional space for housing such equipment.
It is therefore an object of this invention to provide a fine particle removal capability that can be incorporated in known water clarification apparatus.
A more specific object of the invention is to provide a flotation water clarification system capable of continuously removing particles of above a predetermined size, such as for example 100 to 300 microns, from the clarified water without requiring a costly additional installation.
Another object is to provide a fine particle removal capability that can filter either 100%, or some lower percentage, of the total clarified water flow.